HELP: Mille backfiring & running/starting very rough

CHAPLAIN1 · Apr 12, 2016

Subject bike: 02 Mille R

Bike doesnt want to start and when it does it backfires and runs very rough.

>> So far tested/checked the following:
-tested compression
-camshaft to crankshaft timing
-valve clearances
-cam timing sensor
-removed flywheel and checked woodruff key
-crankshaft timing sensor
-tried different ECU and EPROM

*>> Have replaced:
- new battery
- Yamaha solinoid
- MOSFET regulator w weather pac plugs
-complete Sprag clutch replacement
-ground wire to starter
-new sparkplugs

The engine is still backfiring on start up and running rough when I can get it started. At this point I am not sure what to check next.

*

redratbike · Apr 12, 2016

Pull the pump out the tank check the hoses for splits and changed the fuel filter

CHAPLAIN1 · Apr 12, 2016

redratbike said:
Pull the pump out the tank check the hoses for splits and changed the fuel filter

Not a bad idea. Fuel did go bad while it was sitting for another reason.

CHAPLAIN1 · May 18, 2016

OK, problem still present. I gave up and gave the bike to a very reptible ape mechanic who also gave up. Here is a list of the things that have been checked to try and isolate the issue:

>Compression test 185 psi, both cylinders with cold engine

>Cam timing and front to rear phasing is correct

>Checked for excessive play in camshaft drive mechanism

>Valve clearances checed and are all correct

>Flywheel key not damaged, replaced crank timing sensor and flywheel with timing triggers

>Installed a test ECU and EPROM

>Tested camshaft timing sensor per procedure in service manual

>Swapped complete throttle bodies injection and measured fuel pump output pressure

>Measured wiring continuity and connections between sensors and ECU connectors. All ok

HELP

pgdirtman · May 27, 2016

I'm a newbie and helping a friend. 2001 1000. The stock fuel filter has crimped clamps on the hoses. Do I cut them off and replace with aftermarket? His bike revs up and down by itself. I was told to look for any air leaks, replace fuel filter, apply dialectic grease to all connections and replace the small hoses on the left hand side. Also to run some injector cleaner through it. Thanks for any help.

Quinn · May 29, 2016

Possibly throttle position sensor, you can check this with joining two test wires together then power up dash but don't start bike and you should get a code that you can check/google oh test wires are under seat by ecu

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HELP: Mille backfiring & running/starting very rough

CHAPLAIN1

redratbike

CHAPLAIN1

CHAPLAIN1

pgdirtman

Quinn

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